Contribution of personalized dosimetry in dose adjustment of selective internal radiotherapy: Retrospective study of patients treated with ⁹⁰Y- microspheres

Liver tumors have a high mortality and curative treatments are not feasible for all patients. Selective internal radiotherapy (SIRT) or radioembolization with microspheres labelled with Yttrium-90 is widely used for the treatment of patients with liver metastases or primitive liver cancer. The interventional technique requires the embolization of neoplastic microvasculature by way of the deposition of millions of β-emitting microsphere. The objective of SIRT is to deliver irradiation at tumoricidal dose, locally and selectively to the tumor while sparing the healthy hepatic tissue. Despite promising clinical results, there is currently no consensus on the determination of the dose (activity in becquerel). The activity calculation must take into account healthy tissue tolerance criteria and case-by-case response objectives. Beyond this SIRT planning, post-treatment dosimetric estimation is also important in order to assess the therapeutic response in terms of tolerance and treatment efficacy. The objective of this work is to demonstrate the contribution of accurate and personalized dosimetry to optimize planning (predictive dosimetry) and evaluation of SIRT (post-treatment dosimetry). A dosimetric analysis of treatments performed at the Bordeaux University Hospital, mainly in the context of hepatocellular carcinoma using the dosimetry Simplicit90Y^R software to assess doses to the tumor and at-risk tissues (lungs and healthy liver). This study allowed us to analyze tumor control using clinical data but also dosimetric data that were not available at the time of the treatment. The analysis of the dosimetric data allows to optimize the dosage of these treatments but also to define predictive and prognostic factors of SIRT. (author)